1. Faculty of Medicine, Department of Obstetrics and Gynecology Juntendo University Tokyo Japan
2. Department of Social Medicine National Center for Child Health and Development Tokyo Japan
3. Perinatal Center for Maternity and Neonate Yokohama City University Medical Center Yokohama Japan
4. Center for Maternal‐Fetal, Neonatal and Reproductive Medicine National Center for Child Health and Development Tokyo Japan
5. Faculty of Medicine, Department of Obstetrics and Gynecology International University of Health and Welfare Chiba Japan
6. Department of Obstetrics and Gynecology Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Okayama Japan
7. Department of Obstetrics and Gynecology Jichi Medical University Shimotsuke Tochigi Japan
8. Department of Obstetrics Hokkaido University Hospital Sapporo Japan
9. Department of Maternal Fetal Medicine Osaka Women's and Children's Hospital Osaka Japan
10. Department of Obstetrics and Gynecology Hamamatsu University School of Medicine Hamamatsu Japan
11. Faculty Medicine, Department of Obstetrics and Gynecology Mie University Tsu Mie Japan